1. Field of the Invention
The invention relates to a diaphragm device, with which individual wavelengths or ranges of wavelengths in the path of a beam of spectrally dispersed light are suppressed, and is related to the problem of the wavelength selectivity, in particular when using different light sources, or such sources which emit light with a wide range of wavelengths.
2. Description of Related Art
Various diaphragm devices for selective detection or suppression of individual wavelengths in spectrally dispersed light are known in the prior art. The spectrum of the light coming from the sample is at first dispersed, for instance, by means of a prism or a grating, and then falls on the diaphragm device. Of this, individual wavelengths or wavelength ranges are not transmitted; the remaining light passes through the diaphragm and falls in general on a spectrum resolving detector. Alternatively, the spectrum of the transmitted light can also be unified again and deflected to an individual detector, which registers only the intensity. Such spectrally selective diaphragms are used, for example, in fluorescence microscopy or fluorescence spectroscopy. In this method, the sample is marked with dyes. The dyes are excited to fluoresce by means of irradiation with laser light with specific wavelengths. However, a not insignificant part of the excitation light is also reflected or scattered by the sample and reaches into the path of the detection beam. With the help of a wavelength selective diaphragm, one can filter out the excitation light before the detection, so that the measurement is not falsified as a result of it.
The laser systems according to the prior art used in fluorescence microscopy emit only a few fixed wavelengths. For these wavelengths, individual diaphragms can be arranged in fixed positions before the detector. Recently, however, use of broadband emitting and variable broadband laser light sources are gaining importance, because with these sources, a larger spectrum of methods for examination with one and the same microscope is available, without necessitating replacement of the modules. Use of such systems also requires some flexibility in the selection of the excitation wavelengths, whereby these wavelengths must be suppressed before the detection. A diaphragm device with which this type of flexible filtering can be achieved is described, for example, in US 2005/045812 A1. In FIG. 6 of that publication, masks, which suppress a certain spectral range, and which are displaceable parallel to the surface of the detector arrays, are disclosed. Thereby, these masks can be moved in three translational and three rotational degrees of freedom. Such a high number of degrees of freedom requires a complicated mechanical and motor system, which is not described in further detail in the mentioned publication.